Insulated wire and terminal therefor.



A. M. WENTWORTH. IN SULATED WIRE AND TERMINAL THEREFOR.

APPLICATION FILED AUG-24, I914- 1,157,916. Patnted 00t.26,1915.

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manamrsauw Witnesse Inventor-z a. .J h-thurm.Wen worth,

His fitter-ne UNITED STATES ra'rnnrorrrou;

ARTHUR M. WEN'IWORTH, or rrr rsrrnnn, 'MAssAcHUsn'rTs, ASSIGNOR To GENERAL ELECTRIC COMPANYfA .conronn'rron OF 'NEW YORK.

INSULATED WIRE AND TERMINAL THEREFOR.-

9 specification of Letters Patent. tente g t, 2

I Application file} August 24,1914. Serial No. 858,168.

To all whom dim-a concern:

Be it known that I, ARTHUR M. VVrngcr WORTH, a citizen of the United States, re-

" siding at Pit'tsfield, in the county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Insulated Wire and Terminal Therefor, of.

which the following .is a specification.

- My invention has reference to'themanufacture of sheathed wire comprising a re-" sistance conductor embedded in insulating material which is inclosed in Ea metallic sheath; --A successful method for manufacturing wire of this character is, fully disclosed in an application which was filed by Chester Nx Moore', Serial No. 837 ,873, on May 11th, 1914:, to which reference maybe had. for fuller details as 'to manufacture. Briefly, however, it may be stated that wire of this character is now made by first form ing ,a blank or ingot composed of a metal ,core which, when the finished product is to be used for heating purposes, should be of high resistance material; this core is arranged at the center of a metal tube which is ordinarily composed of steel or'copper,. and the'spac'e between the core and the tube is packed with a refractory powdered heat insulating material. which is capable of being compressed ;to a high degree. The whole is then swaged down in a swaging machine until the insulating material is thoroughly compacted and until it reaches a condition resembling, in its physical proper-'- ties, the character of a metal, and the entire unit approximates a condition of homo- When the sheathed ing or by other processes such as rolling or v drawing, until the resistance member is of the required cross-section and until the layer of insulating material between the resistance conductor and the sheath becomes very thin; Now, the resistance conductor of sheathed wire madefin the manner indicated above is of substantially uniform cross-sec;

. tion, and oneof the serious obstacles to the use of sheathed wire of this character has beenthe difliculty of satisfactorily securing terminals from the supply circuitto the resistance wire. When ,plainsheathed. wire I is used the resistance conductor must necessarily project beyond the end of the insulatmg met/anal and s eath, an s the re sistance wire is very small, the manipulation necessary in securing the terminal to the 'wire is' liable to result in the resistance wire being'broken. Furthermore, an operation such as flbrazing'is usually required to .secure theterminal to the resistance wire,

and this causes the resistance wire to become highly heated, and this is liable to result in its crystallization, which may cause it to deteriorate in use. In addition to this, the heat is ;not conducted away from that part of theresistance wire which is bathed in air, and which is adjacent the terminal, as rapidly as it is from the wire which is inclosed in the sheath, and the part of the wire which isadjacent the terminal accordingly runs ata higher temperature than the re- .with anenlarged terminal, preferably integral with the resistance wire.

In its broader aspect, however, my invention has for its object the provision of sheathed wire of the character indicated 4 provided with one or more enlarged sections of the resistance wire at any desired point.

For a fuller understanding of my invention, reference'may be had to the accompanyin-g drawings in .which v l Figure 1 1s a longltudmal, section of a blank or ingot from which the sheathed wire may be made; Fig. .2 is similar to Fig. '1;

but shows theingot reduced in cross-section;

Fig. 3 is similar to Fig. 2, but with the plug at the end removed and the end of the sheath stripped to expose the end of'the' core wire;

Fig. 4 is similar toFig. 3, but with the'end of the sheath reduced to a taper; Fig. 5' shows the process carried a step fartherr, in which the external diaineter of the sheath is uniform and the taper at the end of the sheath transferred to :the inside of the sheath; Fig. 6 is similar to Fig. 5, showing the sheath closed against the metallic core; Fig. 7 shows the wire after a further reduction takes place; Fig. 8 is similar to Fig. 7,

terial stripped so as to expose enough of the but showing the sheathand insulating mato Figs. 1 to 8, which illustratemy inven tion applied to the manufacture of sheathed J duced -by known-processes to a diameter show a modification of my invention in which my process-is applied to the formation a showing the same reduced until the metallic sheath is of a'substantially uniform external diameter; Figs. 11 and 12 show still another.-

modification, in which my: invention is' applied to the formationofanenlarged sectionof the core wire which makes the same particularly suitable for a branched electric 5" connection.

Referring now to the drawings, and first wire provided with an enlarged terminal, 1 in Fig. 1 is a metallic core, usually made of a high resistance material which 'is sufficiently ductile to permit of its I being re-i which makesit suitableas a-resistance conductor. This core is arranged. atthe center" of the metallic tube 2, jthe space between the core and the tube being packed withvrefrac v -tory powdered insulating'm'aterial 3, suchas magnesia or lime. 'Thef-end' of the tube is closed by means ofjp'lugs 4.; The ingot. is

now reduced, preferablyina swaging ma-*' chine. of any suitable} design, until the insulating material is thoroughly compacted and reaches a condition resembling, in its physical characteristics, a metal, at which time the sheathedwire may be bent and treated in general as an ordinary .wire without disturbing the relation of the component parts. This preliminary reduction, should usually j sistancefcore isf rther'reduced, This pr'ocessj results in the f0 mation of an enlarged, terminal 6--1ntegral with the resistance wire,

also be carried to a point where the core wire is of the proper size to forma terminal. The end of the'sheath andthe plugs are then I removed, as indicated in Fig. 3-, one end only being shown, in or'der to bare the core wire. The-end of the sheathed wire is now turned downto a taper, as-at 5, so that the external diameter of the end of the sheath is less than. I the middle, andso that the wall of the sheath is thirlneig at the end than in the middle. The sheathed wire is then, further reduced by swaging why other processes it desir able, such as rolling or- .drawing, as in'clic'ated l in'Fig. '5'. During thiss'tage of the process- '1 the end of the core wire is relieved or par 'tially'relieved of thepressure exerted by the dies or rolls through the insulating material.v :in proportion tothe thickness of the mategv rial that has been removed from'thefouter sheath, with 3 the consequence that the 1 di ameter of the'endof the core wire remains I stage, that is to say, about the same'as that about thesame as it was at the previous shown ln-Fig. 4, while the body of the re it l -f outerishe'a' from the portion of the core where the change in diameter occurs being surrounded by the ins'ulating material. During this reduction,

the taper at the end of the sheath is transferred from the external part'of the sheath to the internal part, as indicated at 7, and the end of the core wire being relieved of the pressure from the dies or rolls in proportion to the thickness of the material that has been removed from thesheath', the end of the core wire takes on a taper corresponding to the taper of the sheath.

While: the succeeding step ofthe process is not absolutely essential to the formation of-satiefactorysheathed wire with an ent:

larged terminal, I prefer to place the end of the sheathed Wire in a die and subject the same to pressure, thereby closing the sheath against the core wire,- as at 8 -(see- Fig. 6). The p'revious operations involved will result in a'certain amount of insulating material being removed from the end of the sheath,

as at 9 ,(see Fig. 5), and with a little experience the operator will be able to ascertain about the amount that should be removed in order .to leave .the insulating material at the endof the sheathed wire, after the sheath has-been closed against the core, of about. the same density as that in the remainder of the sheath. The reduction is now continued until the resistance wire has attained the proper size. With the end of the sheath closed against the resistance wire, thls may be accomplished without-danger of fiurther insulating material being removed from the sheath. Finally, the end of the sheath and the insulating material are removed, leaving a sheathed-wire 'of, .the form shown in F ig. 8 with an ,enlargedterminal'fi', the sheathv having a substantially uniform external 1 diameter, andthe portion of the wire where the-change of cross-section occurs being surrounded by insulating material.

The terminal formed in accordance with th'e' forego ing process may be used directly as 2av 'termlnal, and as the cross-section of thesame is much-greater than that-of the; p

resistance wire, theierminal runs much cooler andthere is-no dangerof the same deteriorating in use v or, if desired, terminals maybe bra-zed, or otherwis'e'secured to this I terminal, without danger of injuring the same. I

a back' and'fforth to forma heating unit, and where it becomes: desirable togsupport the sheathed wire at. theends of the coils. In

" Figs.- 19 land.- I- have illustrated sheathed wire-madei accordance with my invention purpose. e section of the It is sometimes desirable town a section I ,orsections-of the sheathed wire cooler than I which the wire is to be i supported is reduced, as indicated, at P. The sheathed wire is then reduced, and this reduction will result in the formation of an *enlarged'section l0,'as indicated in Fig. 10, and for ;the same reasons as explained in connection with the formation of the enlarged terminal.

Figs. 11 and 12 show my invention applied to theformation of an enlarged section of the core wire, which particularly adapts the same for connection to a branch wire. For this purpose, a small section of the outer sheath 4 is removed, and when tlte sheathed wire is swaged or otherwise reduced a short enlarged section 9 will be .formed on the Wire. 'An opening may now be made in the sheath and insulating material, and an electrical connection be made Whitney, No. 1,093,512, which was issued to the resistance wire at this point. I am aware of a patent grantedjo Willis R.

April '14, 1.914, and I do not herein claim 'fbroadly a sheathed wire provided with an enlarged terminal, or the process of making the same. g I I r Since the only portion of the resistance conductor in the sheathed wire, made in ac-' cordance with my process, which is exposed to the atmosphere, is theenlarged terminal, the wire may be used without danger of the terminals being burned out or broken. The section of the. wire where the change "of .cross-section occurs is surrounded by the refractory insulating material, so that-all of that portion 'of the resistance conductor which is run at a high temperature is en- In accordance with the provisions of the tirely" surrounded by theinsulating material,

oxidized, as the air is excluded.

It will be understood that the terminal formed in accordance with my invention may, if'desired, be surrounded by a jacket filled with refractory insulating material, but ordinarily it will be found that a separate inclosing jacket is unnecessary.

patent statutes, I have described the principle of operation -of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but

,I desire to have it understood that the apparatus shown vis-only illustrative andthat the invention can be carried out by other means.

What I claim as new 'and'desire to secure by Letters Patent of the United States,

tive passesv through a reducing machine and partially relieving the pressure on a portion of the conductor during a stage of'the re ducing" operation and thereby leave the conductor larger in section at said portion.

2 The method of forming a sheathed wire from an ingot in which a conductor is embedded in insulating material surrounded portion is reduced in section less than the main body of the conductor.

7 3. The method of forming sheathed wire I with a conductor of variable cross-section from an ingot in which a conductor of substantially uniform cross-section iscembedded in an insulating material and surrounded by a metallic sheath which consists in forming the metallic sheath with a variable eX- ternal diameter and then reducing the sheathed wire.

4. The method of forming sheathed wire with a conductor having an enlarged terminal from an ingot in which a conductor is embedded in an insulating material surrounded by a metallic sheath which consistsin removing an outer layer fromthe end Q of the sheath and 'then' reducing the sheathed wire.

5. The method of making sheathed wire having an enlarged terminal from an ingot composed of a' metallic core embedded in insulating material surrounded by a me- @1 1 tallic sheath, which consists in removing an outer layer from the end of the sheath to and there is no danger of the same belng swaging down an ingot formed of a metallic coreembedded in insulating material inclosed in a metallic sheath until the core is off a size suitable for a terminal, reducingthe'external diameter of a portion of the sheath, and then reducing the sheathed wire.

7. The methodofmaking sheathed wire which consists in forming a metallic core surrounded by refractory .heatinsulating material inclosed in a metal sheath, reducing the outside diameter of a portion of the sheath and then reducing the sheathed wire.

'8. The method of making sheathed Wire provided with an.enlarged terminal which consists in forming :a metallic core surrounded by refractory heat insulating material inclosed in a. metal sheath, reducing the outside diameter of the end of the sheath and then reducing the sheathed wire. s 9. The method of making sheathed wire provided with an enlarged terminal which consists in forming a metallic core surrounded by refractory heat insulating material inclosed in a metal sheath, reducingl v to a taper and. then reducing the sheathed wire. a z i v 10. The step in the method of making sheathed wire from an ingot comprising ametallic core embedded in powdered insu lating material surrounded by a metallic sheath by swaging, which consists at an intermediate stage of the process in closing the sheath against the core. I

11. As an article of manufacture, sheathed wire comprising a resistance conductor formedwith an enlarged section embedded in refractory insulating material and surroundedby a sheath having a substantially uni'form external diameter, which compacts the material against the conductor.

12. As an article of manufacture, sheathed wire comprising a resistance wire embedded in powdered'refra'ctory insulating material andsurrounded by a metallic sheath which compacts the material against the conductor,

the outside diameter of the end of the sheath l/the resistance conductor being provided with an enlarged terminal, and the sheath having a I substantially uniform external diameter. I v I "/13. As an articleof manufacture, sheathed wire comprising a resistance conductor embedded in refractory insulating material inclosed in a metallic sheath which compacts the material against the conductor, the resistance conductor being provided with an integral enlarged terminal, the portion of the conductor where the change in crosssection occurs being surrounded by thein- 35 sulating material, and the sheath having a substantially uniform external diameter.

' I In witness whereof, I have'hereunto set my'hand this 20th day of August, 1914.

ARTHUR M. WENTWORTH.

Witnesses: Y I

ANNIE R. NUGENT, \QOLIVE L; READ; 

